If a user equipment (UE) needs to transmit data through an LTE network, a bearer needs to be established first. An end-to-end bearer of the LTE network is an evolved packet system (EPS) Bearer, and the EPS Bearer refers to an end-to-end data transmission bearer between a UE and a packet data network (PDN) gateway (P-GW). The EPS Bearer may be further divided into a radio bearer, an S1 Bearer, and an S5/S8 Bearer, where the Radio Bearer refers to a transmission bearer between a UE and a base station (e.g., eNB), the S1 Bearer refers to a UE specific bearer between an eNB and a serving gateway (S-GW) for a specific UE, the S5/S8 Bearer refers to a transmission bearer between an S-GW and a P-GW, and the Radio Bearer and the S1 Bearer are collectively referred to as an evolved radio access bearer (E-RAB) bearer.
After a UE starts up and registers with a network, the network establishes a default bearer for the UE, and after the UE returns to an idle state, the network releases an E-RAB bearer, that is, releases a Radio Bearer and an S1 Bearer. When the UE needs to transmit data, the network needs to establish the Radio Bearer and the S1 Bearer first and then modifies an S5/S8 Bearer, and after these operations are completed, the UE can transmit the data.
In some scenarios, for example, in an intelligent meter reading scenario, in order to improve the transmission efficiency, only the Radio Bearer may be released, and the S1 Bearer and the S5/S8 Bearer are retained, and at the same time, an eNB retains UE context. However, when downlink data is sent from the S-GW to the eNB, the downlink data cannot be sent to the UE because the Radio Bearer has been released, as a result, data loss occurs.